This program is aimed at the development and application of in vivo NMR spectroscopic methods for studying metabolism and its perturbation by chemical toxins. A principal focus of these studies has been the development of NMR active, intracellular indicator, molecules to allow determination of metabolic parameters of interest in intact cells. Research has focused on the use of fluorinated indicators as a consequence of the inherent sensitivity of fluorine for NMR detection and the essential absence of background fluorine resonances from untreated cells. We have previously noted that in NMR studies of suspensions of human erythrocytes to which fluorine-containing molecules have been added, there is generally a significant chemical shift difference between intra- and extracellular indicators. Use was made of this shift difference, to study the distribution of various molecules between intra- and extracellular spaces. We have subsequently initiated studies of the transport of fluorinated nucleosides,, making use of magnetization transfer methods which allow the study of rapidly transported molecules under steady state conditions. Erythrocytes have frequently served as models for transport studies since there is generally a minimum of interference due to other metabolic transformations which can complicate the analysis. In addition, we have recently evaluated the use of perfluorotributylamine (FTBA) as an indicator of partial oxygen pressure in vivo. We are evaluating this technique in the gas-compressed vitrectomized rabbit eye; the high precision of this approach has allowed the rate of oxygen flow into the vitreous to be studied in real time. It was found that the vitreous substitute (FTBA) acts as an oxygen reservoir with a pseudo-first order half life of oxygen elimination from FTBA in the intact eye of roughly 60 minutes. NMR studies of the metabolism of polyphosphates by the protozoan Leishmania major, responsible for causing the disease Leishmania, have also continued.